Microstructural Studies of Alumina Fibre Reinforced Aluminium Alloy

Abstract

The microstructure of alumina fibre reinforced Al-7wt%Si alloy has been studied. The eutectic structure which characterised this alloy was changed by the presence of fibres, with silicon and intermetallic phase tending to segregate on the fibres. The coarse silicon precipitates exhibited twinning but no epitaxial relationship with the aluminium, whilst fine silicon precipitates had a cube-cube orientation with the aluminium lattice. Lath-like intermetallics, FeSiAl₅ and FeSi₂Al₄ with monoclinic and tetragonal structures, existed in equilibrium with a defined epitaxial relationship. Chemical reaction between fibres and matrix was not observed, although magnesium segregation at the fibre surface occurred. Dislocation substructures in the aluminium matrix were also studied.